In motorized vehicle engines, the movement of pistons in the engine and the engine crankshaft may cause the engine to be unbalanced. This can result in vibration of the engine which contributes to decreased engine performance, and may also generate noise which may be annoying or distracting to the driver of the vehicle.
Attempts to address engine vibrations include providing one or more balance shafts within the engine configured to reduce a magnitude of the engine vibrations. One example approach is shown by van Lieshout in U.S. Pat. No. 9,777,775. Therein, a scissor gear is provided on a drive gear assembly of the engine, with the scissor gear attached to the drive gear and arranged coaxially with the drive gear. The teeth of the scissor gear are loaded in an opposite direction to a direction in which the drive gear acts. The loading is accomplished by meshing teeth of the scissor gear with teeth of a weighted balance gear arranged about a balance shaft.
However, the inventors herein have recognized potential issues with such systems. As one example, a torsional relationship between the drive gear and the scissor gear is governed by a force provided by a C-shaped spring inserted between the drive gear and scissor gear and having pins extending from each end. One of the pins extends into the drive gear and the other pin extends into the scissor gear, and so the amount of torque provided between the gears corresponds to the amount of pre-load on the C-shaped spring. However, the amount of pre-load on the C-shaped spring can vary due to parameters which can be difficult to control, such, as properties of the spring itself including material properties, spring thickness, spring dimensions, an amount of heat treatment in manufacturing the spring, etc. Each of the properties of the spring may have variations due to the springs being manufactured with certain tolerances of the properties from batch-to-batch. Additionally, potential variation in the pre-load may arise from a positional variation of the holes in one or both of the drive gear and scissor gear configured to receive the pins of the spring.
In one example, the issues described above may be addressed by an adjustable drive gear assembly, comprising: a first gear; a second gear arranged coaxially with the first gear; a first pin engaged with the first gear and having a first projecting portion; a second pin engaged with the second gear and having a second projecting portion; and a planar C-shaped spring extending between the first projecting portion of the first pin and the second projecting portion of the second pin to couple the first gear to the second gear and provide a torsional load therebetween, wherein at least one of the first and second projecting portions is non-round and rotatable to vary the length of the spring. In this way, the pre-load of the spring may be adjusted via the pins without replacement of the spring or other components of the engine.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.